71 VIN Series and Tag Date Code

[Tom R.]

this question rose on another forum and caught my curiosity. I encouraged the owner to post here and show up for the Indy Regional...but here's his stuff:

"I have a 71 car with VIN ending in 118294. Trim tag on car is J28 (May 28, 1971). The judging manual that I have says that last serial number for May 1971 was 118223. I am trying to determine if there is chance that something has been altered on my car.

May 28, 1971 was a Friday and should have been the last production day in May since Monday May 31, 1971 was Memorial day.

My manual indicates that serial numbers for June 1971 should range from 118224 through 120686, which averages about 120 cars for each of the 22 production days in June 1971.

Accordingly, if my manual is correct regarding the serial cut off for May 1971 being 118223, then since my serial number is 71 higher, I would expect the tag to read K1 (or Tuesday June 1, 1971).

So basically, it appears that my tag is one production day different than would be expected based upon the literature I have."

I offered alternative explanations including the worker forgot to change the dies in the stamp jig the day after Memorial Holiday and did not catch it until later that day.

[Michael W.]

Re: 71 VIN Series and Tag Date Code

I'll take a shot at it- the tags were stamped and attached long before the car were considered complete ie.- off the line. This one was still sitting on the line over the May 28-31 time period and only rolled off June 1. It got counted as June production, not May.

[Kent K.]

Re: 71 VIN Series and Tag Date Code

Rick --- Gene is right on. Terry McManmon indicated to me that my '69 with an Aug. 6th date may have come off the line 1 to 3 days after, if memory serves me.
Kent #6201

[Michael W.]

Re: 71 VIN Series and Tag Date Code

Thanks Bill!

[Kent K.]

Memory gone!!!

Please accept my appologies Tom and Mike.
Kent #6201

[Michael W.]

LOL! *NM*

[Tom R.]

Re: 71 VIN Series and Tag Date Code

Mike:

I'm not sure what Kent was referring to but I understand your comment to mean that the trim tag build date will always differ from the monthly production numbers because the latter is determined at the point when the car rolls out the back door.

In contrast, the trim tag is stamped and riveted in place at the start of the Trim Line in 1971...so as indicated it has 1-3 days before getting to the back door. If I understand correctly...this is a good point of clarification.

[Mark Milner]

Body date and final assembly are not the same

Those numbers are the last VIN for that month to go to the parking lot. It is not the date they were welded or riveted to the body.

This has been very obvious in the midyears where the A. O. Smith bodies were often many days different, but even some St. Louis bodies were a day or two off.

The C3 bodies were more in line with the time, however, end of shift means any sitting on the line when they shut down will not be counted as finally assembled (born) until the next work day when it rolls past the final inspection.

In the case of an end of month body, the VIN can often be recorded the first day of the following month.

In this case, there were around 60 cars between it and the last May car, so that places it easily in the first work day of June.

To understand, you really need to visit a car assembly line.

To some degree, it is like many restored Corvettes. Is the day it is reborn the day you fire the engine in the bare chassis, the day you drop the body on the chassis, or the day you drive it out of the garage the first time? Now realized that dates were assigned at each step, so firing your engine could be June 20, 2005, dropping the body could be August 12, 2005, and driving it out of the garage could be January 20, 2006.

[Tom R.]

Yet so much emphasis place on trim tag build date

Good points! Yet the build date is the single published source of production that is a constant over the decades. All of which must be understood when interpreting build dates. Look at a late model C3 build sheet and you than have the "estimated build date" as well to factor into the mix of dates.

[Mark Milner]

Re: Yet so much emphasis place on trim tag build d

The only "facts" you can associate with the body build date are this:

1. This was the date when they attached the body tag to the birdcage/body. (Even this is speculation, as what if they had a bunch made and the line stopped, so bodies at the end of the day didn't get their tag on time that day but rather the next day.)

2. The car was not released as a car before that date. (Wasn't built yet.) It may have been released that date AT THE EARLIEST but most likely after by a day, except with midyears where you have the A. O Smith issue and bodies sometimes got delayed.

3. Strikes, line shutdowns, and breakage could all alter the time between when a body tag was installed and when the car rolled off the end of the line on its own power.

[Terry M.]

more variables

You guys have covered some of the variables well, but allow me to throw in another.
I am told by former GM employees that what was counted as a complete car changed over the years -- that is it was not always "out the door to the parking lot." Sometimes it was engine start, and other times roll off the end of the line. Not that they changed this standard daily, or even yearly -- but over the many years of Corvette production at what point the accountants counted the car complete did change. I would bet there were fudge factors for start and end of model year production as well.
None of those differences will in most cases matter a great deal to us looking at production from this vantage point of 25 or 50 years in the future, but we should know that we can not split these hairs too finely lest they all fall apart.

[John H.]

Re: more variables

In a conventional assembly plant, a car is counted as "produced" when it rolls off the Final Line and heads for the roll test/toe-in machines. St. Louis had TWO Final Lines - the first was the main line, where the car was driven off and roll-tested/toed-in (but the car had no interior soft trim in it), and the second was at the end of the Final Trim Line (after water test), where the carpets, seats, door trim panels, etc. were installed - the car went from there to shipping. Don't know for sure which line was used for "the count", but I suspect it was the first one, where it came off the main line.